Cancer is one of the leading causes of death in the US. Chemotherapy remains an important cancer treatment modality. Traditionally, cytotoxic molecules that activate only a single tumor-killing mechanism are used. Combination chemotherapy is now a common practice, which involves treating patients with several medicines that differ in their killing mechanisms. Gemcitabine is approved for the treatment of various carcinomas: pancreatic, breast, lung, and bladder cancers. Although it is extremely potent in tumor cells in culture, the clinical outcomes of gemcitabine in patients is rather modest, and recent pre-clinical data indicated that a gemcitabine-in-liposome formulation helped improve the efficacy of gemcitabine. A recent new development is the use of synthetic double-stranded RNA (dsRNA) as a potential chemotherapy agent. Certain dsRNA molecules have multiple direct and indirect pro-apoptotic, anti-proliferative, and anti-angiogenic activities. Interestingly, our recent data showed that the anti-tumor activity of a locally injected synthetic dsRNA was significantly enhanced when the dsRNA was dosed in combination with systemically dosed gemcitabine, indicating that a combination therapy using gemcitabine and dsRNA represents a promising tumor therapy approach. However, local peritumoral injection is clinically impractical for the majority of tumors. We propose to develop epidermal growth factor (EGF)-conjugated, long-circulating, nanometer-scale liposomal dsRNA formulation and gemcitabine formulation to target them into EGF receptor-over-expressing tumor cells after intravenous injection and to validate the resultant anti-tumor activity in mouse models of mouse or human cancers. To accomplish our overall goal, we propose the following three specific aims: (i) to engineer EGF-coated, long-circulating liposomal carriers for a synthetic dsRNA and for gemcitabine and to validate their activities in vitro, (ii) to evaluate the extent to which the liposomal carriers will deliver the dsRNA and/or the gemcitabine into model tumors in mice after intravenous injection, and (iii) to evaluate the extent to which a combination therapy using tumor-targeting liposomal dsRNA and gemcitabine will inhibit the tumor growth in vivo. The completion of this application will lay a solid scientific foundation for us to devise strategies to improve the clinical outcome of cancers sensitive to dsRNA and gemcitabine in the future. A similar strategy can also be adopted to combine dsRNA with other chemotherapy agents to fight other tumors. PUBLIC HEALTH RELEVANCE: Many tumor cells over-express the EGF receptor. The successful engineering of EGF-conjugated, long- circulating liposomal synthetic dsRNA and liposomal gemcitabine and the validation of their anti-tumor activities when given in combination will lay a sound scientific foundation for future improvement of the clinical outcomes of tumors sensitive to both gemcitabine and dsRNA. A similar strategy can also be utilized to fight other cancers by combining dsRNA with other chemotherapy agents.